Method for preparing molecular SSZ-81

ABSTRACT

The present invention is directed to a method for preparing a new crystalline molecular sieve designated SSZ-81 using a structure directing agent selected from 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications, 1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dications, and mixtures thereof.

This application claims the benefit of U.S. Provisional Application No.61/358,806, filed Jun. 25, 2010.

FIELD OF THE INVENTION

The present invention relates to method of making new molecular sieveSSZ-81 in a hydroxide media using a structure directing agent (“SDA”)selected from 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications,1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dications, and mixturesthereof.

BACKGROUND OF THE INVENTION

Molecular sieves are a class of important materials used in the chemicalindustry for processes such as gas stream purification and hydrocarbonconversion processes. Molecular sieves are porous solids havinginterconnected pores of different sizes. Molecular sieves typically havea one-, two- or three-dimensional crystalline pore structure havingpores of one or more molecular dimensions that selectively adsorbmolecules that can enter the pores, and exclude those molecules that aretoo large. The pore size, pore shape, interstitial spacing or channels,composition, crystal morphology and structure are a few characteristicsof molecular sieves that determine their use in various hydrocarbonadsorption and conversion processes.

For the petroleum and petrochemical industries, the most commerciallyuseful molecular sieves are known as zeolites. A zeolite is analuminosilicate having an open framework structure formed from cornersharing the oxygen atoms of [SiO₄] and [AlO₄] tetrahedra. Mobile extraframework cations reside in the pores for balancing charges along thezeolite framework. These charges are a result of substitution of atetrahedral framework cation (e.g. Si⁴⁺) with a trivalent or pentavalentcation. Extra framework cations counter-balance these charges preservingthe electroneutrality of the framework, and these cations areexchangeable with other cations and/or protons.

Synthetic molecular sieves, particularly zeolites, are typicallysynthesized by mixing sources of alumina and silica in an aqueous media,often in the presence of a structure directing agent or templatingagent. The structure of the molecular sieve formed is determined in partby solubility of the various sources, silica-to-alumina ratio, nature ofthe cation, synthesis conditions (temperature, pressure, mixingagitation), order of addition, type of templating agent, and the like.

Although many different crystalline molecular sieves have beendiscovered, there is a continuing need for new molecular sieves withdesirable properties for gas separation and drying, hydrocarbon andchemical conversions, and other applications. New molecular sieves maycontain novel internal pore architectures, providing enhancedselectivities in these processes.

SUMMARY OF THE INVENTION

The present invention is directed to a new family of molecular sieveswith unique properties, referred to herein as “molecular sieve SSZ-81”or simply “SSZ-81.”

In accordance with the present invention there is provided a molecularsieve having a mole ratio greater than about 10 of silicon oxide toaluminum oxide and having, after calcination, the powder X-raydiffraction (XRD) lines of Table 4.

The present invention further includes a method for preparing acrystalline material by contacting under crystallization conditions: (1)at least one source of silicon; (2) at least one source of aluminum; (3)at least one source of an element selected from Groups 1 and 2 of thePeriodic Table; (4) hydroxide ions; and (5) a structure directing agentselected from 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications,1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dications, and mixturesthereof.

The present invention also includes a process for preparing a molecularsieve having, after calcination, the powder XRD lines of Table 4, by:

(a) preparing a reaction mixture containing: (1) at least one source ofsilicon; (2) at least one source of aluminum; (3) at least one source ofan element selected from Groups 1 and 2 of the Periodic Table; (4)hydroxide ions; (5) a structure directing agent selected from1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications,1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dications, and mixturesthereof; and (6) water; and

(b) maintaining the reaction mixture under conditions sufficient to formcrystals of the molecular sieve.

Where the molecular sieve formed is an intermediate material, theprocess of the present invention includes a further post-synthesisprocessing in order to achieve the target molecular sieve (e.g. by acidleaching in order to achieve a higher silica to alumina (Si:Al) ratio).

The present invention also provides a novel molecular sieve designatedSSZ-81 having a composition, in the as-synthesized and anhydrous state,in terms of mole ratios, as follows:

Broadest Secondary SiO₂/Al₂O₃ 10-60 20-35 (Q + A)/SiO₂ 0.02-0.100.04-0.07 M/SiO₂ 0.01-1.0  0.02-0.04wherein:

(1) M is selected from the group consisting of elements from Groups 1and 2 of the Periodic Table;

(2) Q is at least one 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentanedication structure directing agent, and Q≧0; and

(3) A is at least one 1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentanedication structure directing agent, and A≧0.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the results of a powder X-ray diffraction (XRD) analysis ofthe as-synthesized molecular sieve prepared in Example 1.

FIG. 2 shows the results of a XRD analysis of the calcined molecularsieve of Example 2.

DETAILED DESCRIPTION OF THE INVENTION Introduction

The term “Periodic Table” refers to the version of IUPAC Periodic Tableof the Elements dated Jun. 22, 2007, and the numbering scheme for thePeriodic Table Groups is as described in Chemical and Engineering News,63(5), 27 (1985).

The term “molecular sieve” includes (a) intermediate and (b) final ortarget molecular sieves and molecular sieves produced by (1) directsynthesis or (2) post-crystallization treatment (secondary synthesis).Secondary synthesis techniques allow for the synthesis of a targetmaterial having a higher Si:Al ratio from an intermediate material byacid leaching or other similar dealumination methods.

Where permitted, all publications, patents and patent applications citedin this application are herein incorporated by reference in theirentirety, to the extent such disclosure is not inconsistent with thepresent invention.

Unless otherwise specified, the recitation of a genus of elements,materials or other components, from which an individual component ormixture of components can be selected, is intended to include allpossible sub-generic combinations of the listed components and mixturesthereof. Also, “include” and its variants, are intended to benon-limiting, such that recitation of items in a list is not to theexclusion of other like items that may also be useful in the materials,compositions and methods of this invention.

Reaction Mixture

The present invention is directed to a molecular sieve designated hereinas “molecular sieve SSZ-81” or simply “SSZ-81.”

In preparing SSZ-81, a 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentanedication, a 1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dication, or amixture thereof, is used as a structure directing agent (“SDA”), alsoknown as a crystallization template. The SDAs useful for making SSZ-81are represented by the following structures (1) and (2):

In general, SSZ-81 is prepared by:

(a) preparing a reaction mixture containing (1) at least one source ofsilicon; (2) at least one source of aluminum; (3) at least one source ofan element selected from Groups 1 and 2 of the Periodic Table; (4)hydroxide ions; and (5) a structure directing agent selected from1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications,1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dications, and mixturesthereof; and

(b) maintaining the reaction mixture under conditions sufficient to formcrystals of the molecular sieve.

Where the molecular sieve formed is an intermediate material, theprocess of the present invention includes a further step of synthesizinga target molecular sieve by post-synthesis techniques, such as acidleaching.

The composition of the reaction mixture from which the molecular sieveis formed, in terms of molar ratios, is identified in Table 1 below:

TABLE 1 Reactants Broad Secondary SiO₂/Al₂O₃ molar ratio 20-80 25-35M/SiO₂ molar ratio 0.05-0.30 0.10-0.20 (Q + A)/SiO₂ molar ratio0.05-0.30 0.10-0.20 OH⁻/SiO₂ molar ratio 0.20-0.60 0.30-0.35 H₂O/SiO₂molar ratio 10-50 30-40wherein compositional variables Q, A and M are as described hereinabove.

Sources useful herein for silicon include fumed silica, precipitatedsilicates, silica hydrogel, silicic acid, colloidal silica, tetra-alkylorthosilicates (e.g. tetraethyl orthosilicate), and silica hydroxides.

Sources useful for aluminum include oxides, hydroxides, acetates,oxalates, ammonium salts and sulfates of aluminum. Typical sources ofaluminum oxide include aluminates, alumina, and aluminum compounds suchas AlCl₃, Al₂(SO₄)₃, aluminum hydroxide (Al(OH₃)), kaolin clays, andother zeolites. An example of the source of aluminum oxide is LZ-210 andLZ-52 zeolite (types of Y zeolites).

As described herein above, for each embodiment described herein, thereaction mixture may be formed using at least one source of an elementselected from Groups 1 and 2 of the Periodic Table (referred to hereinas M). In one subembodiment, the reaction mixture is formed using asource of an element from Group 1 of the Periodic Table. In anothersubembodiment, the reaction mixture is formed using a source of sodium(Na). Any M-containing compound which is not detrimental to thecrystallization process is suitable. Sources for such Groups 1 and 2elements include oxides, hydroxides, nitrates, sulfates, halogenides,oxalates, citrates and acetates thereof.

The SDA dication is typically associated with anions (X⁻) which may beany anion that is not detrimental to the formation of the zeolite.Representative anions include elements from Group 17 of the PeriodicTable (e.g., fluoride, chloride, bromide and iodide), hydroxide,acetate, sulfate, tetrafluoroborate, carboxylate, and the like.

The 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dication SDA of thepresent invention (represented by structure (1)) can be synthesized byreacting a dihaloalkane (such as 1,5-dibromopentane) with1-azonia-bicyclo[2.2.2]octane. The1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dication SDA of thepresent invention (represented by structure (2)) can be synthesized byreacting a dihaloalkane (such as 1,5-dibromopentane) with1,4-diazabicyclo[2.2.2]octane.

For each embodiment described herein, the molecular sieve reactionmixture can be supplied by more than one source. Also, two or morereaction components can be provided by one source.

The reaction mixture can be prepared either batch wise or continuously.Crystal size, morphology and crystallization time of the molecular sievedescribed herein may vary with the nature of the reaction mixture andthe synthesis conditions.

Crystallization and Post-Synthesis Treatment

In practice, the molecular sieve is prepared by:

(a) preparing a reaction mixture as described herein above; and

(b) maintaining the reaction mixture under crystallization conditionssufficient to form the molecular sieve. (See, Harry Robson, VerifiedSyntheses of Zeolitic Materials, 2^(nd) revised edition, Elsevier,Amsterdam (2001)).

The reaction mixture is maintained at an elevated temperature until themolecular sieve is formed. The hydrothermal crystallization is usuallyconducted under pressure, and usually in an autoclave so that thereaction mixture is subject to autogenous pressure, at a temperaturebetween 125° C. and 200° C.

The reaction mixture may be subjected to mild stirring or agitationduring the crystallization step. It will be understood by a personskilled in the art that the molecular sieves described herein maycontain impurities, such as amorphous materials, unit cells havingframework topologies which do not coincide with the molecular sieve,and/or other impurities (e.g., organic hydrocarbons).

During the hydrothermal crystallization step, the molecular sievecrystals can be allowed to nucleate spontaneously from the reactionmixture. The use of crystals of the molecular sieve as seed material canbe advantageous in decreasing the time necessary for completecrystallization to occur. In addition, seeding can lead to an increasedpurity of the product obtained by promoting the nucleation and/orformation of the molecular sieve over any undesired phases. When used asseeds, seed crystals are added in an amount between 1% and 10% of theweight of the source for silicon used in the reaction mixture.

Once the molecular sieve has formed, the solid product is separated fromthe reaction mixture by standard mechanical separation techniques suchas filtration. The crystals are water-washed and then dried to obtainthe as-synthesized molecular sieve crystals. The drying step can beperformed at atmospheric pressure or under vacuum.

The molecular sieve can be used as-synthesized, but typically will bethermally treated (calcined). The term “as-synthesized” refers to themolecular sieve in its form after crystallization, prior to removal ofthe SDA cation. The SDA can be removed by thermal treatment (e.g.,calcination), preferably in an oxidative atmosphere (e.g., air, gas withan oxygen partial pressure of greater than 0 kPa) at a temperaturereadily determinable by one skilled in the art sufficient to remove theSDA from the molecular sieve. The SDA can also be removed by photolysistechniques (e.g. exposing the SDA-containing molecular sieve product tolight or electromagnetic radiation that has a wavelength shorter thanvisible light under conditions sufficient to selectively remove theorganic compound from the molecular sieve) as described in U.S. Pat. No.6,960,327 to Navrotsky and Parikh, issued Nov. 1, 2005.

The molecular sieve can subsequently be calcined in steam, air or inertgas at temperatures ranging from about 200° C. to about 800° C. forperiods of time ranging from 1 to 48 hours, or more. Usually, it isdesirable to remove the extra-framework cation (e.g. Na⁺) byion-exchange or other known method and replace it with hydrogen,ammonium, or any desired metal-ion.

Where the molecular sieve formed is an intermediate material, the targetmolecular sieve can be achieved using post-synthesis techniques to allowfor the synthesis of a target material having a higher Si:Al ratio froman intermediate material by acid leaching or other similar dealuminationmethods.

The molecular sieve made from the process of the present invention canbe formed into a wide variety of physical shapes. Generally speaking,the molecular sieve can be in the form of a powder, a granule, or amolded product, such as extrudate having a particle size sufficient topass through a 2-mesh (Tyler) screen and be retained on a 400-mesh(Tyler) screen. In cases where the catalyst is molded, such as byextrusion with an organic binder, the molecular sieve can be extrudedbefore drying, or, dried or partially dried and then extruded.

The molecular sieve catalyst of the present invention can optionally becombined with one or more catalyst supports, active base metals, othermolecular sieves, promoters, and mixtures thereof. Examples of suchmaterials and the manner in which they can be used are disclosed in U.S.Pat. No. 4,910,006, issued May 20, 1990 to Zones et al., and U.S. Pat.No. 5,316,753, issued May 31, 1994 to Nakagawa.

Catalyst supports combinable with SSZ-81 include alumina, silica,zirconia, titanium oxide, magnesium oxide, thorium oxide, berylliumoxide, alumina-silica, amorphous alumina-silica, alumina-titanium oxide,alumina-magnesium oxide, silica-magnesium oxide, silica-zirconia,silica-thorium oxide, silica-beryllium oxide, silica-titanium oxide,titanium oxide-zirconia, silica-alumina-zirconia, silica-alumina-thoriumoxide, silica-alumina-titanium oxide or silica-alumina-magnesium oxide,preferably alumina, silica-alumina, clays, and combinations thereof.

Exemplary active base or noble metals useful herein include thoseselected from the elements from Group 6 through Group 10 of the PeriodicTable, their corresponding oxides and sulfides, and mixtures thereof. Inone subembodiment, each base or noble metal is selected from the groupconsisting of nickel (Ni), palladium (Pd), platinum (Pt), cobalt (Co),iron (Fe), rhenium (Re), chromium (Cr), molybdenum (Mo), tungsten (W),and mixtures thereof. In another subembodiment, the hydroprocessingcatalyst contains at least one Group 6 base metal and at least one basemetal selected from Groups 8 through 10 of the periodic table. Exemplarymetal combinations include Ni/Mo/W, Mi/Mo, Mo/W, Co/Mo, Co/W and W/Ni.

Promoters include those selected from phosphorous (P), boron (B),silicon (Si), aluminum (Al), and mixtures thereof.

SSZ-81 is useful in catalysts for a variety of hydrocarbon conversionreactions such as hydrocracking, fluidized catalytic cracking (FCC),hydroisomerization, dewaxing, olefin isomerization, alkylation ofaromatic compounds and the like. SSZ-81 is also useful as an adsorbentfor separations.

In one embodiment, SSZ-81 is used in a hydroisomerization process whichincludes the step of contacting SSZ-81, typically in the hydrogen formcontaining a noble metal such as platinum, palladium or a mixturethereof, with a feed containing C₄-C₇ linear and branched paraffins,under hydroisomerization conditions. In one particular subembodiment, ahydroisomerization process is provided which includes the step ofcontacting molecular sieve SSZ-81 based catalyst with a feed containingC₄-C₇ linear and branched paraffins, under hydroisomerization conditionssufficient to yield a liquid product having a higher research octanenumber (RON), as determined by ASTM D2699-09, than the feed.

The feed is typically a light straight run fraction, boiling within therange of 30° F. to 250° F. (−1° C. to 121° C.), for example from 60° F.to 200° F. (16° C. to 93° C.). The isomerization reaction is typicallycarried out in the presence of hydrogen. Hydrogen may be added to give ahydrogen-to-hydrocarbon molar ratio (H₂/HC) of between 0.5 and 10H₂/HC,for example between 1 and 8H₂/HC. Typically, the feed is contacted withSSZ-81 (or a catalyst containing SSZ-81) at a temperature in the rangeof from about 150° F. to about 700° F. (65.5° C. to 371° C.), at apressure ranging from about 50 psig to about 2000 psig (0.345 MPa to13.9 MPa gauge pressure), and a feed liquid hour space velocity (LHSV)ranging from about 0.5 to about 5 h⁻¹. See U.S. Pat. No. 4,910,006 andU.S. Pat. No. 5,316,753 for a further discussion of isomerizationprocess conditions.

A low sulfur feed is useful in the present process. The feed desirablycontains less than 10 ppm, for example less than 1 ppm or less than 0.1ppm sulfur. In the case of a feed which is not already low in sulfur,acceptable levels can be reached by hydrotreating the feed in apretreatment zone with a hydrotreating catalyst which is resistant tosulfur poisoning. See the aforementioned U.S. Pat. No. 4,910,006 andU.S. Pat. No. 5,316,753 for a further discussion of thishydrodesulfurization process.

It is typical to limit the nitrogen level and the water content of thefeed. Catalysts and processes which are suitable for these purposes areknown to those skilled in the art.

After a period of operation, the catalyst can become deactivated bysulfur or coke. See the aforementioned U.S. Pat. No. 4,910,006 and U.S.Pat. No. 5,316,753 for a further discussion of methods of removing thissulfur and coke, and of regenerating the catalyst.

The conversion catalyst desirably contains one or more Group 8-10metals. The Group 8-10 noble metals and their compounds, platinum,palladium, and iridium, or combinations thereof can be used. Rhenium andtin may also be used in conjunction with the noble metal. Typically, themetal is platinum or palladium. The amount of Group 8-10 metal presentin the conversion catalyst should be within the normal range of use inhydroisomerizing catalysts, from about 0.05 to 2.0 weight percent, forexample 0.2 to 0.8 weight percent.

Characterization of the Molecular Sieve

Molecular sieves made by the process of the present invention have acomposition, in the as-synthesized and anhydrous state, as described inTable 2 (in terms of mole ratios), wherein compositional variables Q, Aand M are as described herein above.

TABLE 2 Broadest Secondary SiO₂/Al₂O₃ 10-60 20-35 (Q + A)/SiO₂ 0.02-0.100.04-0.07 M/SiO₂ 0.01-1.0  0.02-0.04

Molecular sieves synthesized by the process of the present invention arecharacterized by their XRD pattern. The powder XRD pattern lines ofTable 3 are representative of as-synthesized SSZ-81 made in accordancewith this invention. Minor variations in the diffraction pattern canresult from variations in the mole ratios of the framework species ofthe particular sample due to changes in lattice constants. In addition,sufficiently small crystals will affect the shape and intensity ofpeaks, leading to significant peak broadening. Minor variations in thediffraction pattern can also result from variations in the organiccompound used in the preparation and from variations in the Si/Al moleratio from sample to sample. Calcination can also cause minor shifts inthe XRD pattern. Notwithstanding these minor perturbations, the basiccrystal lattice structure remains unchanged.

TABLE 3 Characteristic XRD Peaks for As-Synthesized SSZ-81 2 Theta^((a))d-spacing (Angstroms) Relative Intensity (%)^((b))  7.02 12.58 W  7.4111.91 M 7.41 peak-10.50^((c)) W, broad band 18.50-22.03 peak^((d)) W,broad band 22.03 4.03 W-M 22.58 3.94 S 23.30 3.81 W 24.12 3.69 W 25.103.55 W 27.30 3.26 W 28.55 3.12 W ^((a))±0.20 ^((b))The powder XRDpatterns provided are based on a relative intensity scale in which thestrongest line in the X-ray pattern is assigned a value of 100: W(weak)is less than 20; M(medium) is between 20 and 40; S(strong) is between 40and 60; VS(very strong) is greater than 60. ^((c),(d))In the pattern foras-synthesized SSZ-81, it can be seen that there is a firstlow-intensity (W), broad-band running from the peak near 2θ = 7.4degrees down to baseline at near 2θ = 10.5 degrees, and a secondlow-intensity, broad-band rising from the baseline at about 2θ = 18.5degrees and then merging into a well-defined peak just beyond 22degrees. This behavior is seen in all samples of as-synthesized SSZ-81.

The X-ray diffraction pattern lines of Table 4 are representative ofcalcined SSZ-81 made in accordance with this invention.

TABLE 4 Characteristic XRD Peaks for Calcined SSZ-81 2 Theta^((a))d-spacing (Angstroms) Relative Intensity (%)^((b))  7.45 11.86 S 7.45peak-10.50^((c)) W, broad band 14.38 6.15 W 18.50-22.26 peak^((d)) W,broad band 22.26 3.99 W 22.79 3.90 S 23.53 3.78 W-M 24.36 3.65 W-M 25.373.51 W 26.37 3.38 W 27.53 3.24 W 28.67 3.11 W ^((a))±0.20 ^((b))Thepowder XRD patterns provided are based on a relative intensity scale inwhich the strongest line in the X-ray pattern is assigned a value of100: W(weak) is less than 20; M(medium) is between 20 and 40; S(strong)is between 40 and 60; VS(very strong) is greater than 60. ^((c),(d))Inthe pattern for calcined SSZ-81, it can be seen that there is a firstlow-intensity (W), broad-band running from the peak near 2θ = 7.4degrees down to baseline at near 2θ = 10.5 degrees, and a secondlow-intensity, broad-band rising from the baseline at about 2θ = 18.5degrees and then merging into a well-defined peak just beyond 22degrees. This behavior is seen in all samples of calcined SSZ-81.

The powder X-ray diffraction patterns presented herein were collected bystandard techniques. The radiation was CuK-α radiation. The peak heightsand the positions, as a function of 2θ where θ is the Bragg angle, wereread from the relative intensities of the peaks (adjusting forbackground), and d, the interplanar spacing in Angstroms correspondingto the recorded lines, can be calculated.

EXAMPLES

The following examples demonstrate but do not limit the presentinvention.

Example 1 Synthesis of SSZ-81 Using1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane Dication

5.0 g of a hydroxide solution of1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane ([OH⁻]=0.4 mmol/g) wasadded to a Teflon container. Next, 0.18 g of zeolite Y-52 (as providedby Union Carbide Corp.), 1.50 g of a 1N NaOH solution and 0.50 g ofwater was added to the container. Finally, 0.50 g CAB-O-SIL M-5 fumedsilica (Cabot Corporation) was slowly added and the gel was thoroughlymixed. The Teflon liner was then capped and sealed within a steel Parrautoclave. The autoclave was placed on a spit within a convection ovenat 160° C. The autoclave was tumbled at 43 rpm over the course of 17days in the heated oven. The autoclave was then removed and allowed tocool to room temperature. The solids were then recovered by filtrationand washed thoroughly with deionized water. The solids were allowed todry at room temperature.

The resulting product was analyzed by powder XRD. FIG. 1 shows thepowder XRD pattern of the as-synthesized product of this Example. Table5 below shows the powder X-ray diffraction lines for the resultingproduct.

TABLE 5 2 Theta^((a)) d-spacing (Angstroms) Relative Intensity (%)  6.1414.38 8.1  7.02 12.58 2.2  7.41 11.91 27.0 7.41 peak-10.50^((b))low-intensity, broad band 18.50-22.03 peak^((c)) low-intensity, broadband 11.08 7.98 3.3 12.86 6.88 2.9 15.57 5.69 4.1 18.72 4.74 4.9 22.034.03 21.4 22.58 3.94 100.00 23.30 3.81 13.8 24.12 3.69 14.2 25.10 3.556.3 26.12 3.41 3.9 26.36 3.38 4.4 27.30 3.26 7.8 28.55 3.12 8.6 31.292.86 5.0 33.94 2.64 1.8 34.08 2.63 2.6 36.69 2.45 3.4 ^((a))±0.20^((b),(c))In the pattern for as-synthesized SSZ-81, it can be seen thatthere is a first low-intensity (W), broad-band running from the peaknear 2θ = 7.4 degrees down to baseline at near 2θ = 10.5 degrees, and asecond low-intensity, broad-band rising from the baseline at about 2θ =18.5 degrees and then merging into a well-defined peak just beyond 22degrees. This behavior is seen in all samples of as-synthesized SSZ-81.

Example 2 Calcination of SSZ-81

The product of Example 1 was calcined inside a muffle furnace under aflow of 2% oxygen/98% nitrogen heated to 595° C. at a rate of 1° C./minand held at 595° C. for five hours, cooled and then analyzed by powderXRD. The resulting XRD pattern is shown in FIG. 2. Table 6 below showsthe powder XRD lines for the calcined molecular sieve product.

TABLE 6 2 Theta^((a)) d-spacing (Angstroms) Relative Intensity (%)  7.4511.86 89.1 7.45 peak-10.50^((b)) low-intensity, broad band  9.85 8.977.5 11.62 7.61 6.7 14.38 6.15 7.3 18.50-22.26 peak^((c)) low-intensity,broad band 22.26 3.99 15.5 22.79 3.90 100.00 23.53 3.78 21.9 24.36 3.6519.4 25.37 3.51 7.6 26.37 3.38 13.3 26.69 3.34 5.5 27.53 3.24 10.4 28.673.11 6.1 ^((a))±0.20 ^((b),(c))In the pattern for calcined SSZ-81, itcan be seen that there is a first low-intensity (W), broad-band runningfrom the peak near 2θ = 7.4 degrees down to baseline at near 2θ = 10.5degrees, and a second low-intensity, broad-band rising from the baselineat about 2θ = 18.5 degrees and then merging into a well-defined peakjust beyond 22 degrees. This behavior is seen in all samples of calcinedSSZ-81.

The XRD pattern indicates that the material remains stable aftercalcination to remove the organic SDA.

Example 3 NH₄ ⁺ Exchange

Ion-exchange of calcined SSZ-81 material (prepared in Example 2) isperformed using NH₄NO₃ to convert the molecular sieve from its Na⁺ formto the NH₄ ⁺ form, and, ultimately, the H⁺ form. Typically, the samemass of NH₄NO₃ as the molecular sieve is slurried in water at a ratio of25-50:1 water to zeolite. The exchange solution is heated at 95° C. for2 hours and then filtered. This procedure can be repeated up to threetimes. Following the final exchange, the molecular sieve is washedseveral times with water and dried. This NH₄ ⁺ form of SSZ-81 can thenbe converted to the H⁺ form by calcination (as described in Example 2)to 540° C.

Example 4 Constraint Index

0.5 grams of calcined H⁺ form material prepared per Example 3, in a20-40 pelletized and meshed range, was loaded into a stainless steelreactor (glass wool packing on both sides of the catalyst bed) and runin a Constraint Index test (50% n-hexane/50% 3-methylpentane (3-MP)). Anormal feed rate was used (8 μl/min.) and a first test was run at 260°C. (500° F.) and a second test was run at 316° C. (600° F.). Each testwas run after the catalyst had been dried in the reactor to near 538° C.(1000° F.). Helium flow was used. (See, Zones and Harris, Microporousand Mesoporous Materials 35-36 (2000), pp. 31-46.)

As shown in Tables 7 and 8, at 10 minutes on-stream, ˜92% of the feedwas being converted with approximately equal amounts of each reactant inthe first test, and in the second test over 99% of the feed was beingconverted with about equal amounts of each reactant.

TABLE 7 n-C₆ conversion (%) 89.7 3-methylpentane conversion (%) 95.1Feed conversion (%) 92.4 Constraint Index (including 2-MP) 1.05Constraint Index (excluding 2-MP) 0.75 MP = methylpentane

TABLE 8 n-C₆ conversion (%) 99.3 3-MP (%) 99.2 Feed conversion (%) 99.3Constraint Index (including 2-MP) 1.21 Constraint Index (excluding 2-MP)1.03 MP = methylpentane

Example 5 Adsorption of 2,2-Dimethylbutane

The calcined material of Example 3 was then tested for the uptake of thevapor of hydrocarbon 2,2-dimethylbutane. This adsorbate does not entersmall pore zeolites (8-ring portals) and sometimes is hindered inentering intermediate pore zeolites like ZSM-5. The SSZ-81 showed aprofile characteristic of a multi-dimensional, large-pore material (suchas Y zeolite), showing rapid uptake and high pore filling.

At P/Po of ˜0.3 and at room temperature, SSZ-81 was shown to adsorb over0.18 cc/gram after 15 minutes of exposure to the vapor of2,2-dimethylbutane adsorbate, and about 0.19 cc/gram after about 1 hourof exposure to the adsorbate.

Example 6 Synthesis of SSZ-81 Using a Combination of Dications

1.25 g of a hydroxide solution of1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane ([OH⁻]=0.40 mmol/g) and3.75 g of a hydroxide solution of1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane ([OH⁻]=0.41 mmol/g) wereadded to a Teflon container. Next, 0.18 g of zeolite Y-52 (provided byUnion Carbide Corporation), 1.50 g of a 1N NaOH solution and 0.50 g ofwater were added to the container. Finally, 0.50 g CAB-O-SIL M-5 fumedsilica (Cabot Corporation) was slowly added and the gel was thoroughlymixed. The Teflon liner was then capped and sealed within a steel Parrautoclave. The autoclave was placed on a spit within a convection ovenat 160° C. The autoclave was tumbled at 43 rpm over the course of fourweeks in the heated oven. The autoclave was then removed and allowed tocool to room temperature. The solids were then recovered by filtrationand washed thoroughly with deionized water. The solids were allowed todry at room temperature.

The resulting product was analyzed by powder XRD. The XRD analysisindicated the product was SSZ-81.

Example 7 Synthesis of SSZ-81 Using a1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane Dication

5.0 g of a hydroxide solution of1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane ([OH⁻]=0.41 mmol/g) wasadded to a Teflon container. Next, 0.18 g of zeolite Y-52 (provided byUnion Carbide Corp), 1.50 g of a 1N NaOH solution and 0.50 g of waterwere added to the container. Finally, 0.50 g CAB-O-SIL M-5 fumed silica(Cabot Corporation) was slowly added and the gel was thoroughly mixed.The Teflon liner was then capped and sealed within a steel Parrautoclave. The autoclave was placed on a spit within a convection ovenat 160° C. The autoclave was tumbled at 43 rpm over the course of sixweeks in the heated oven, with periodic interruption to look for productformation. The autoclave was then removed after 6 weeks and allowed tocool to room temperature. The solids were then recovered by filtrationand washed thoroughly with deionized water. The solids were allowed todry at room temperature.

The resulting product was analyzed by powder XRD. The XRD analysisindicated the product was a mixture of SSZ-81 and some remainingunreacted zeolite Y-52.

Example 8 Preparation of Hydroisomerization Catalyst

Al-SSZ-81 in H⁺-form prepared in accordance with the procedure outlinedin Example 3 herein, was ion-exchanged with an aqueous (NH₃)₄Pd(NO₃)₂solution at pH of ˜10.3 to load the zeolite with 0.5 wt % Pd. ThePd/Al-SSZ-81 molecular sieve was then calcined in air at 450° F. (232°C.) for 5 hours, and subsequently reduced in hydrogen prior to thecatalytic experiment set forth in Example 9.

Example 9 n-Hexane Hydroisomerization over Pd/Al-SSZ-81

The catalytic reaction of hydroisomerization of n-hexane was carried outusing the Pd/SSZ-81 catalyst prepared in Example 8 herein, in aflow-type fixed bed reactor with pure n-hexane as the feed. Thehydroisomerization conditions included a pressure of 200 pounds persquare inch gauge (psig)(1.38 MPa gauge pressure), a liquid hour spacevelocity (LHSV) of 1 h⁻¹, and a H₂ to hydrocarbon molar ratio of 6:1.The reaction temperatures ranged from 400 to 620° F. (204-327° C.) in10° F. (5.5° C.) increments. The reaction products were analyzed with anon-line gas chromatograph to quantify all the cracking and isomerizationproducts. Representative results are shown in Table 9.

TABLE 9 Temperature 500° F. 520° F. (260° C.) (271° C.) n-Hexaneconversion (mol %) 18.99 80.84 Cracking yield (mol %) 0.03 1.28Isomerization yield (mol %) 18.96 79.56 Distribution 2,2-dimethyl-butane0.64 11.90 of branched 2,3-dimethyl-butane 5.26 12.45 C₆ paraffin2-methyl-pentane 58.22 45.94 isomers 3-methyl-pentane 35.88 29.71 (mol%) Total 100.0 100.0

What is claimed is:
 1. A method for preparing molecular sieve SSZ-81,comprising contacting under crystallization conditions (1) at least onesource of silicon; (2) at least one source of aluminum; (3) at least onesource of an element selected from Groups 1 and 2 of the Periodic Table;(4) hydroxide ions; and (5) a structure directing agent selected from1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications,1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dications, and mixturesthereof; wherein the molecular sieve has, after calcination, an X-raydiffraction pattern substantially as shown in the following Table:d-spacing 2 Theta (Angstroms) Relative Intensity (%)  7.45 ± 0.20 11.86S 7.45 peak-10.50, ±0.20 W, broad band 14.38 6.15 W 18.50-22.26 peak,±0.20 W, broad band 22.26 ± 0.20 3.99 W 22.79 ± 0.20 3.90 S 23.53 ± 0.203.78 W-M 24.36 ± 0.20 3.65 W-M 25.37 ± 0.20 3.51 W 26.37 ± 0.20 3.38 W27.53 ± 0.20 3.24 W 28.67 ± 0.20 3.11 W.


2. The method of claim 1, wherein the molecular sieve is prepared from areaction mixture comprising, in terms of mole ratios, a composition asdescribed in the following Table: SiO₂/Al₂O₃ 20-80 M/SiO₂ 0.05-0.30 (Q +A)/SiO₂ 0.05-0.30 OH⁻/SiO₂ 0.20-0.60 H₂O/SiO₂ 10-50

wherein: (1) M is selected from the group consisting of elements fromGroups 1 and 2 of the Periodic Table; (2) Q is at least one1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dication structuredirecting agent, and Q≧0; and (3) A is at least one1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dication structuredirecting agent, and A≧0.
 3. The method of claim 1, wherein themolecular sieve has a composition, as-synthesized and in the anhydrousstate, in terms of mole ratios, as follows: SiO₂/Al₂O₃ 10-60 (Q +A)/SiO₂ 0.02-0.10 M/SiO₂ 0.01-1.0 

wherein: (1) M is selected from the group consisting of elements fromGroups 1 and 2 of the Periodic Table; (2) Q is at least one1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dication structuredirecting agent, and Q≧0; and (3) A is at least one1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dication structuredirecting agent, and A≧0.
 4. The method of claim 2, wherein themolecular sieve has a composition, as-synthesized and in the anhydrousstate, in terms of mole ratios, as follows: SiO₂/Al₂O₃ 20-35 (Q +A)/SiO₂ 0.04-0.07 M/SiO₂ 0.02-0.04

wherein: (1) M is selected from the group consisting of elements fromGroups 1 and 2 of the Periodic Table; (2) Q is at least one1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dication structuredirecting agent, and Q≧0; and (3) A is at least one1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dication structuredirecting agent, and A≧0.
 5. The method of claim 1, wherein themolecular sieve is prepared from a reaction mixture comprising, in termsof mole ratios, a composition as described in the following Table:SiO₂/Al₂O₃ 25-35 M/SiO₂ 0.10-0.20 (Q + A)/SiO₂ 0.10-0.20 OH⁻/SiO₂0.30-0.35 H₂O/SiO₂ 30-40

wherein: (1) M is selected from the group consisting of elements fromGroups 1 and 2 of the Periodic Table; (2) Q is at least one1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dication structuredirecting agent, and Q≧0; and (3) A is at least one1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dication structuredirecting agent, and A≧0.